1. Field of the Invention
The present invention relates generally to a power sharing amplifier system; and more particularly, related to a power sharing amplifier system for a cellular communication system.
2. Description of the Prior Art
FIG. 1A shows an 8 by 8 cellular transmitter configuration generally indicated as 100 similar to that shown and described in U.S. patent application Ser. No. 08/683,735. The 8 by 8 cellular configuration 100 includes eight separate low power transmitters generally indicated 102, an 8th order transform matrix circuit 104, eight amplifiers generally indicated 106, an 8 by 8 inverse transform matrix circuit 108, and eight antennas generally indicated as 110.
FIG. 1B shows a mapping of each input port to a respective output port in the 8th order cellular configuration.
FIG. 1C shows a chart of phase shifts for the 8th order transform matrix circuit 104 and the 8th order inverse transform matrix circuit 108 in the 8 by 8 cellular configuration.
When configured as shown, there is only one output (antenna) port for each input (low power transmitter) port, as shown in the mapping of FIG. 1B.
The amplification sharing technique used in the 8 by 8 cellular configuration 100 offers some advantages over the amplification technique of the standard cellular configuration. For example, in the 8 by 8 cellular configuration 100, the amplifiers 108 effectively share the amplification of all the input signals, which provide inherent redundancy in the overall amplification of the input signals. Thus, if one amplifier fails, then all sectors still operate and maintain communication between the subscriber and the land mobile radio system. In such a case, the 8 by 8 cellular configurations 100 may be operating in a less desirable operating mode, but nevertheless it still operates and allows additional time for the failed amplifier to be repaired or replaced. Moreover, the 8 by 8 cellular configuration 100 also uses fewer amplifiers than the standard cellular configuration if redundant amplifiers are maintained for each sector. These advantages combine to make the improved cellular configuration 100 less expensive and more reliable than the standard cellular configuration.
However, one disadvantage of the 8 by 8 cellular configuration 100 shown is that the amplification sharing technique results in intermodulation products between the eight input signals to the various amplifiers that distort the amplified RF output signal sent to and transmitted by the antenna 110.